It is known that infections with bacterial pathogens are increasing globally and that antibacterial resistance is a general health problem in this connection. A worldwide increase in tuberculosis infections due to mycobacterial strains which, over the course of time, has become resistant to the usual therapeutic agents (B. R. Bloom, J. L. Murray, Science 257, 1992, 1055), and the treatment of infections due to multi-resistant staphylococci (M. Kresken, Bundesgesundheitsblatt [Federal Health Newspaper] 38, 1996, 170), make it necessary to design new active substances. Alternative active compounds, possessing new mechanisms of action, in particular for counteracting antibiotic resistance and for controlling bacterial infections when there is intolerance towards existing active compounds, are urgently required. While a significant advance in controlling life-threatening infections was achieved with the development of highly selective nucleoside and nucleotide virustatic agents, such as acyclovir, penciclovir, ganciclovir, sorivudine and cidofovir for herpes viruses, these therapeutic agents all have the same principle of action. They inhibit the viral DNA polymerase. Another disadvantage of these compounds is that they also interfere with the DNA metabolism of the infected cell and therefore harbor the risk of inducing mutagenic, teratogenic and oncogenic effects (Wutzler, P. Thust, R. Antiv. Res. 49, 2001, 55). Furthermore, when nucleoside and nucleotide virustatic agents have been used over long periods, resistance to these medicaments has been shown to develop both in infected cell cultures and in immunosuppressed patients (Andrei, G. et al. Antimicrob. Agents Chemother., 1995, 39, 1632; Pavic, I. et al. Antimicrob. Agents Chemother., 1997, 39, 2686). For this reason, it is necessary to additionally develop novel highly active antiviral prophylactic and therapeutic agents which have another mechanism of action.
The large group of biologically active substances includes quaternary ammonium compounds. They are able to destroy microorganisms such as bacteria and fungi. Low molecular weight quaternary ammonium salts are used as disinfectants or biocidal coating materials (J. Controlled Release 50, 1998, 145). A typical problem associated with the low molecular weight compounds is inadequate bioavailability which is caused, for example, by a variety of transport and breakdown processes. Polymeric quaternary amine-functionalized materials can be synthesized from commercial quaternary exchange resins, by the graft polymerization of polyurethanes with polybutadiene hydroxytelecheles or from polysiloxanes possessing primary alcohol functions in the side chain. These biocidal polymers usually have high production costs and are frequently toxic since they contain residues of the toxic monomers (Trends in Polymer Science 4, 1996, 364). In addition to this, the polymers may accumulate in an undesirable and dangerous manner in the body since they are not biologically degradable. Furthermore, synthetic polymers which contain cationic functions are used as dispersions for preserving wood (U.S. Pat. No. 5,049,383). Disadvantages of the synthetic polymers which contain cationic functions are the high costs of preparing them, their toxicity (contamination with residual monomer) and their stability towards biological degradation.
Polysaccharide derivatives possessing quaternary ammonium functions are known and have thus far been used, in particular, as surface improvement additives for the paper and textile industries and as consistency regulators in cosmetics, in connection with which they only have a low degree of substitution (DS) of <0.2. To date, nothing is known about their biological effects. On the other hand, starch ethers which contain long alkyl chains (C8-C22) and are bonded to the starch by way of silyl ether groups are reported to have antiinfective effects, especially antibacterial effects (JP 05295002). The low chemical stability of the alkyl silyl ethers of polysaccharides leads to an uncontrolled release of functional groups simply as a result of the effect of atmospheric moisture and consequently to a reduction in, or to the loss of, the biological activity (D. Klemm et al., Comprehensive Cellulose Chemistry, Wiley-VCH, 1998). In addition to this, low molecular weight silyl compounds are toxic. In addition, publications refer to cellulose fibers and chitosan derivatives which possess antibacterial activity (W. H. Daly, M. M. Guerrini, Polym. Mat. Sci. Eng. 79, 1998, 220). As a natural cationic polysaccharide, chitosan is the one which is most frequently described and is used as a fungicidal agent in cosmetics (T. Tashiro, Macromol. Mater. Eng. 286, 2001, 63, K. C. Gupta, M. N. V. R. Kumar, J. M. S.-Rev. Macromol. Chem. Phys. C40, 2000, 273). Disadvantages of these polysaccharides are that they are frequently contaminated with other biogenic substances, that they are expensive as a result of the elaborate isolation and purification methods required and their inherent structure, with the ammonium groups being exclusively located on the polymer backbone. In addition to this, it is not possible to control their distribution and the content is limited to a degree of substitution of 1. Superabsorbers composed of cationically modified and crosslinked polysaccharides such as cellulose (EP 0 582 624 B1) have also been described.
While there are statements in the literature to the effect that the biological activity results from the presence of the quaternary ammonium functions, it is reported, on the other hand, that, as can be shown, typical compounds possessing cationic tetra-alkylnitrogen groups, such as polyquaternium 10, do not possess any bioactivity (W. A. Daly, M. M. Guerrini, D. Culberson, J. Macossay, in: Science and Technology of Polymers and Advanced Materials, Plenum Press 1998, 493). It is in no way possible to conclude from the results which are available in the literature whether the structures, and if so which, are in fact biologically active.